Title:
Ocean Currents
(Oceanography)
Grade Level(s): 6-8
Introduction: Currents are moving masses of ocean water on the surface or deep within the oceans.
Wind is the primary force for surface currents. Deep ocean circulation happens because of density differences within water masses. Regular intermittent currents that respond to movement of the sun and moon
are called tidal currents. Tides are the actual rise and fall in local water levels. Every current, regardless of
its origin, has a set and a drift (speed). Set is the true direction toward which a current flows, drift is its
speed.
Learner Objectives:
•
The student will be able to identify the forces that cause surface currents.
•
The student will be able to explain the factors which affect deep ocean currents
Sunshine State Standards: Science: SC.D.1.3.3 Math: MA.B.1.3.2.
Competency-Based Curriculum: Science: Sci. M/J3 III-4-A
Math: M/J3 II-4-A
Materials:
Metal pan(10cm. X 3cm. X 7cm.)
Hair dryer
Pepper
World Map
Activity Procedures:
1. Ask the students a question regarding the direction in which rivers flow (rivers flow in one
direction).
2. Ask how an oceans flow is similar or different than that of a river (waves and tides cause water in
oceans to move up and down and into the shoreline and back to sea).
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Activity Procedures (Cont’d):
3. Ask what they think would happen if someone sealed a message in a bottle, and threw it into
an ocean (most likely the bottle would be found by a person from a distant place).
4. How do you think that the bottle got there? Some students may know that currents carried
the bottle to its present location.
5. Identify to the class that large streams of water moving through an ocean is a current.
6. Identify that currents can move water at the surface or deep within the ocean.
7. Ask the students to distinguish between both types of currents. Surface currents, can be as
deep as several hundred meters below the surface. Deep-ocean currents can be found deeper
than a few hundred meters.
8. Ask what causes surface currents. The wind as the driving force should be the response. To
show this concept the teacher should demonstrate with a shallow pan of water, a hair dryer and
pepper. Sprinkle the pepper on top of the surface of the water in the pan. Then turn on the
blow-dryer and blow the pepper across the surface of the water.
9. Ask if the students can make an inference about ocean currents and the flow of the pepper
across the pan.
Student Assessment:
Have students demonstrate their understanding of ocean currents by writing a story describing the
imaginary trip taken by a bottle which contains a message written by the student.
Activity Extensions:
Have students investigate how surface currents affect the climate of certain landmasses (Miami and the
Gulf Stream would make an ideal investigation).
Home Learning Activity:
Have students investigate the Coriolis’ Effect on the moving water.
Vocabulary: density, tidal currents, set, drift
References/Related Links:
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/sea/htg.rxml
http://www.boatus.com/onlinecourse/documents/environment.html
http://www.odysseyexpeditions.org/oceanography.html
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Ocean Currents
Reading Passage
The waters of the ocean are in constant motion. Its movement ranges from strong currents such as the
Gulf Stream, down to small swirls or eddies. The Sun drives oceanic circulation in two primary ways:
Circulation of the atmosphere; causing variations in the temperature and salinity of seawater, which in turn
control its density. If surface water becomes more dense than the underlying waters, an unstable situation
develops and the denser surface water will sink. This vertical density-driven circulation is known as Thermohaline circulation.
The rotation of the Earth contributes to ocean circulation patterns. The frictional coupling between
the ocean’s waters and the solid Earth is weak. The same is true for air masses. Only very close to the surface
of the Earth is frictional coupling significant. In the extreme case of a projectile moving above the surface of
the Earth, the frictional coupling is zero. The Earth rotates at a constant rate. The apparent deflection of
objects which move over the surface of the Earth without being frictionally bound to it (such as missiles, or
water and air), is explained in terms of an apparent force known as the Coriolis force. The magnitude of the
Coriolis force increases from zero at the equator to a maximum at the poles. The Coriolis force acts at right
angles to the direction of motion, so as to cause a deflection to the right in the Northern Hemisphere and
to the left in the Southern Hemisphere. Because a missile is moving so fast, the amount that the Earth has
“turned beneath” it during its short flight is small. Winds and ocean currents, on the other hand, are slow
moving, and so are significantly affected by the Coriolis force. Consider an ocean current flowing at 1 knot
at 45 degrees north latitude. The water will travel about 1800 meters in an hour the Coriolis force will have
deflected it about 300m from its original path.
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Ocean Currents
FCAT Questions
Directions: Read the passage, then answer the questions. Answer multiple choice questions by circling
the letter of the answer that you select. Write your answer to the “Read, Think, and Explain” question on
the lines provided.
1. Variations in the temperature and salinity of seawater will control which of the
factors?
A.
B.
C.
D.
Mass
Density
Volume
Specific gravity
Answer:
B
2. Thermohaline circulation is defined as:
A.
B.
C.
D.
Frictional coupling between the ocean waters
Constant rotation of the earth.
Apparent deflection of objects
Vertical density-driven circulation
Answer:
D
3. The Sun drives oceanic circulation by:
A. Atmospheric circulation
B. Projectile motion
C. Coriolis force
D. Density differences
Answer:
A
4. Explain how the Coriolis force affects ocean currents
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